Recently, a standard by which various devices can be used at once only by connecting them by wires (cables) and products having this standard installed are put into practical use. For example, PictBridge (CIPA DC-001) by which printing can be performed by connecting a digital camera and printer by a cable called a USB (Universal Serial Bus) is standardized.
When a digital camera and printer using this standard are used, the printer becomes capable of printing when connected by the USB, and printing can be performed only by designating an image to be printed by using the user interface of the digital camera (the digital camera has a liquid crystal display for checking sensed images and the like and various keys).
On the other hand, demands for changing wired information transmission into radio information transmission by using a radio communication method based on the International Standard IEEE 802.11 are increasing, and radio communication is beginning to be used in communication between peripheral devices such as a digital camera, storage device, and printer. Radio communication requires no cable installation, and thereby increases the degree of freedom of the setting location of each device and improves the portability.
A predetermined communication mode, a predetermined ID (ESS-ID), and a predetermined channel for designating a frequency band are set in this radio communication apparatus. Communication is established in a communication network by matching the settings of another apparatus, i.e., a client apparatus in the communication network with these settings such as the communication mode. Note that the communication modes include the “Ad-Hoc mode (peer to peer)” by which a communication network is constructed only by devices having radio LAN cards installed, and the “infrastructure mode” which connects to the existing network via an access point of a repeater in a communication network.
In a network using the same ESS-ID, encrypted communication using a WEP key is performed. The WEP key is key information for encrypting or decrypting data to be transmitted or received. Since data can be exchanged only between radio communication apparatuses in which the same WEP key is set, a leak of the contents of communication to a radio communication apparatus which does not know the WEP key can be prevented. The technique as explained above is disclosed in Japanese Patent Laid-Open No. 2004-202779.
Even when the WEP key described above is used, however, a radio communication apparatus in the same radio network can intercept the contents of communication.
That is, as shown in FIG. 3, assume a radio LAN including access point AP1 (31) and radio communication terminals ST1 (32), ST2 (33), ST3 (34), and ST4 (35). In this radio LAN, radio communication between the individual radio communication terminals is performed in a mode in which radio communication is performed via access point AP1, i.e., in the infrastructure mode. Also, this radio LAN uses the same communication channel, the same ESS-ID, and the same WEP key. If data is exchanged by radio communication between radio communication terminals ST1 and ST2, for example, radio communication terminal ST3 using the same ESS-ID and the same WEP key can intercept the contents of this radio communication.
Generally, a configuration like this is presumably used when a radio LAN is installed in an office. However, even when private data exchange is to be performed between two radio communication terminals, e.g., even when printing is to be performed from a digital camera to a printer by radio communication, it is necessary to connect to the radio LAN by using a predetermined ESS-ID and a predetermined WEP key.
In addition, when a radio communication terminal connects to a radio LAN installed in an office, this radio communication terminal must receive broadcast packets steadily transmitted from another radio communication apparatus, and correctly return packets if necessary. If many radio communication terminals exist or a radio communication terminal which transmits a large amount of packets exists in a radio communication network, communication between these radio communication apparatuses may interfere with data transmitting and receiving operations.